The invention relates to improvements in diaphragm pumps, and more particularly to improvements in means for absorbing or intercepting noise which is generated by the diaphragm of a diaphragm pump.
As a rule, the diaphragm of a diaphragm pump is reciprocated by the connecting rod of a drive wherein the connecting rod receives motion from an orbiting eccentric. Reference may be had, for example, to commonly owned German Pat. No. 30 05 834 to Heinz Riedlinger. The marginal portion of the diaphragm is clamped in the housing and the central portion of the diaphragm is connected with the head of the connecting rod. It is also known to employ so-called dual or twin diaphragm pumps with two housings and an electric motor between the housings. Such diaphragm pumps are often used as vacuum pumps or as compressors.
A drawback of conventional diaphragm pumps is that their diaphragms generate pronounced noise. Noise is generated as a result of oscillations which are imparted by the connecting rod as well as due to natural or characteristic vibrations of the diaphragm. The natural or characteristic vibrations develop in response to pressure changes in the pumping chamber of the diaphragm pump.
Heretofore known proposals to reduce the noise emission of diaphragm pumps include total encapsulation of the diaphragm and of the moving means therefor. This applies particularly for that chamber of a diaphragm pump which contains the eccentric and the means for orbiting the eccentric so that the latter enables the connecting rod to oscillate the central portion of the diaphragm. Encapsulation of the diaphragm and of the drive means for the diaphragm brings about a pronounced reduction of noise. However, if the moving means for the diaphragm is fully encapsulated, it cannot be adequately cooled or cannot be cooled to an optimum extent. This, in turn, prevents the diaphragm from raising the pressure of conveyed fluid media above a relatively low maximum permissible value because a further rise of pressure would entail excessive heating of the diaphragm and of the parts which are adjacent to it. The situation is aggravated in the aforementioned dual or twin diaphragm pumps because it is practically impossible to adequately ventilate the electric motor between the two chambers for the eccentrics and other means for oscillating the respective diaphragms.
On the other hand, proper soundproofing of diaphragm pumps is highly desirable, especially when such pumps are put to use in laboratories and similar establishments which are occupied by engineers, scientists, technicians and other persons involved in mental work. A diaphragm pump is likely to raise its noise emission by up to 40 percent whenever the pressure in the pumping chamber changes from superatmospheric to subatmospheric or vice versa. This can seriously affect the occupants of the facility in which the diaphragm pump is put to use, especially if the facility employs numerous pumps and is occupied by a number of persons whose work and comfort are greatly affected by pronounced fluctuations in noise.